Answer
$\color{blue}{(3x-2x^2)\sqrt[4]{x^2y^3}}$
Work Step by Step
Simplify each radical.
Factor the radicand so that one factor is a perfect fourth power, then bring out the fourth root of the perfect fourth power factor to obtain:
$=\sqrt[4]{81x^4(x^2y^3)}-\sqrt[4]{16x^8(x^2y^3)}
\\=\sqrt[4]{3^4x^4(x^2y^3)} - \sqrt[4]{2^4(x^2)^4(x^2y^3)}
\\=3x\sqrt[4]{x^2y^3}-2x^2\sqrt[4]{x^2y^3}$
Combine like terms to obtain:
$\\=\color{blue}{(3x-2x^2)\sqrt[4]{x^2y^3}}$